Cystatin C in serum as an early marker of renal involvement in Familial Mediterranean Fever patients

BACKGROUND: The major renal involvement in Familial Mediterranean Fever (FMF) is the occurrence of amyloidosis that primarily affects the kidneys manifested by proteinuria and ending in death from renal failure. AIM: This study aims to investigate whether serum cystatin (cys-C) levels could be used as an early marker of renal involvement in FMF patients. PATIENTS AND METHODS: Forty-six patients with FMF during the attack period (AP), and 41 patients with FMF during attack-free periods (AFP), and 11 patients with FMF associated amyloidosis, and 38 healthy controls were enrolled in the study. We determined cys-C levels in the serum of FMF patients and healthy controls. RESULTS: Serum cys-C levels were significantly increased in patients with FMF and secondary amyloidosis, and serum cys-C is a more accurate and efficient marker for detecting renal involvement than estimated glomerular filtration rate (e-GFR) in patients with FMF. CONCLUSIONS: We propose a cutoff level of the serum cys-C of 876.5 pg/mL for screening renal involvement in patients with FMF, and amyloidosis should be strongly suspected when the serum cys-C reaches 1565.5 pg/mL.